## Influence of root parallelism on the stability of extraction-site closures

## Kelly Chiqueto, Guilherme Janson, Carina Thaís de Almeida, Juliana Moura Storniolo, Sérgio Estelita Barros, and José Fernando Castanha Henriques. Am J Orthod Dentofacial Orthop 2011;139:e505-e510

I **ntroduction: **In premolar extraction cases, root parallelism is recommended to preserve the stability of space closures. The influence of the degree of root parallelism on relapse of tooth extraction spaces has been a controversial topic in the literature. The aim of this study was to compare the angle between the long axes of the canine and the second premolarin patients with and without stability of extraction-space closures. **Methods: **A sample of 56 patients, treated with 4 premolar extractions, was divided into 2 groups: group 1, consisting of 25 patients with reopening of extraction spaces; and group 2, consisting of 31 patients without reopening of extraction spaces. Panoramic radiographs of each patient were analyzed at the posttreatment and 1-year posttreatment stages. The data were statistically analyzed by using chi-square tests, t tests, analysis of variance (ANOVA), and Pearson correlation coefficients. **Results: **The results showed that the groups did not differ regarding the angle between the canine and the second premolar, and there was no correlation between angular changes and reopening of extraction spaces, showing that dental angular changes are not determining factors for relapse, and other factors should be investigated. **Conclusions: **The final angle and the posttreatment changes observed in the angle between the long axes of the canine and the second premolar showed no influence on the relapse of extraction spaces.

## Airway volume for different dentofacial skeletal patterns

## Hakan El and Juan Martin Palomo. Am J Orthod Dentofacial Orthop 2011;139:e511-e521

I **ntroduction: **Our objective was to evaluate the nasal passage (NP) and oropharyngeal (OP) volumes of patients with different dentofacial skeletal patterns. **Methods: **The study sample consisted of 140 patients (70 boys, 70 girls), divided into 3 groups as Class I (1 ≤ANB ≤3), Class II (ANB >3), and Class III (ANB <1), and then further divided into 4 groups as SNA angle ≥80°, SNA angle <80°, SNB angle ≥78°, and SNB angle <78° to evaluate how the positional changes in the maxilla and the mandible affect the OP and NP variables. Differences between groups were determined by using the Kruskal-Wallis test. Correlations between the variables were tested with the Spearman correlation coefficient. The linear multiple regression test was applied to create a model for the airway volumes separately. **Results: **The OP volume of the Class II subjects (n = 50) was significantly lower when compared with that of the Class I (n = 46) and Class III subjects (n = 44). The only statistically significant difference for NP volume was observed between the Class I and Class II groups. The mean OP airway volume of subjects with retruded mandibular positions was statistically significantly smaller when compared with the subjects with higher SNB angles. The area of the most constricted region at the base of the tongue (minAx) had a high potential in explaining the OP volume, whereas the NP volume models were not as successful as the OP counterpart. However, minAx was also entered into the NP volume equations as an explanatory variable. **Conclusions: **The OP airway volumes of Class II patients were smaller when compared with Class I and Class III patients. It was observed that mandibular position with respect to cranial base had an effect on the OP airway volume. The only significant difference for the NP volume was between the Class I and Class II groups, with a smaller volume observed for the Class II group.

## Airway volume for different dentofacial skeletal patterns

## Hakan El and Juan Martin Palomo. Am J Orthod Dentofacial Orthop 2011;139:e511-e521

I **ntroduction: **Our objective was to evaluate the nasal passage (NP) and oropharyngeal (OP) volumes of patients with different dentofacial skeletal patterns. **Methods: **The study sample consisted of 140 patients (70 boys, 70 girls), divided into 3 groups as Class I (1 ≤ANB ≤3), Class II (ANB >3), and Class III (ANB <1), and then further divided into 4 groups as SNA angle ≥80°, SNA angle <80°, SNB angle ≥78°, and SNB angle <78° to evaluate how the positional changes in the maxilla and the mandible affect the OP and NP variables. Differences between groups were determined by using the Kruskal-Wallis test. Correlations between the variables were tested with the Spearman correlation coefficient. The linear multiple regression test was applied to create a model for the airway volumes separately. **Results: **The OP volume of the Class II subjects (n = 50) was significantly lower when compared with that of the Class I (n = 46) and Class III subjects (n = 44). The only statistically significant difference for NP volume was observed between the Class I and Class II groups. The mean OP airway volume of subjects with retruded mandibular positions was statistically significantly smaller when compared with the subjects with higher SNB angles. The area of the most constricted region at the base of the tongue (minAx) had a high potential in explaining the OP volume, whereas the NP volume models were not as successful as the OP counterpart. However, minAx was also entered into the NP volume equations as an explanatory variable. **Conclusions: **The OP airway volumes of Class II patients were smaller when compared with Class I and Class III patients. It was observed that mandibular position with respect to cranial base had an effect on the OP airway volume. The only significant difference for the NP volume was between the Class I and Class II groups, with a smaller volume observed for the Class II group.